Introduction to SIMSAT
SIMSAT (Simulation Infrastructure for the Modeling of SATellites) simulation infrastructure is able to host a spacecraft and ground segment simulation. In order to define simulator models without direct reference to any particular simulation infrastructure or hardware environment, the Simulation Model Interface (SMI) was introduced and in SIMSAT, being an SMI compliant environment, the SMI is used as the interface between the simulation and ground models. At the moment, a version of SIMSAT for Windows is available, although a project is currently on going to port the infrastructure to Linux and CORBA (Common Object Request Broker Architecture) rather than Microsoft's COM (Component Object Model) technology.
Simulation Model Interface (SMI)
The SMI is a standard defined by ESA to aid portability of simulation models developed within the European Space Industry. The SMI defines a standard Run-Time Interface that models use to communicate with one another and with the simulation environment. It also presents a set of guidelines for the development of portable models.
The SIMSAT Kernel provides support for the construction and the aggregation of all the SIMSAT Kernel components. An instance of the SIMSAT Kernel plus the simulation models is a complete running simulation. Multiple instances of the MMI can connect to a single instance of the SIMSAT Kernel for control and monitoring of the simulation. Multiple instances of the Kernel framework can exist simultaneously, each containing its own simulation. To be able to support a simulation, the SIMSAT Kernel is made up of several components, which are discussed in brief below.
- Scheduler is responsible for the co-ordination and processing of all events within the Simulation Kernel. An event on the schedule identifies an action that needs to be performed at a specified point in simulated time.
- Mode Manager is the simulation state machine. The Simulation has a number of operational modes, which control the operation of the simulation.
- Time-Manager is responsible for maintaining and providing models and the MMI with the correct simulation-Time. It provides time in four formats, Simulation-Time, Epoch-Time, Zulu-Time and Correlated Zulu-Time. this is a family of SIMSAT compatible models enabling a realistic simulations
- Logger supports the recording of Kernel or model events that occur during a simulation. The log in which the current simulation messages are written is called the active log. The logger also provides a view of the simulation event history in an MMI during a simulation session.
- Visualization manager is responsible for making the values of both model and Kernel data items available for display in an MMI.
- State-vector manager is responsible for the saving and restoring of the state of the simulation. Its main purpose is to allow the Simulation State, at any point in the simulation, to be saved. This allows the user to return to an earlier simulation scenario.
- Command handler is responsible for the reception and execution of Kernel and user defined commands.a set of generic space models that ease the developments of the spacecraft models used in operational.
- Command procedure interpreter is responsible for the interpretation of command procedures. A command procedure contains Kernel and User defined simulator commands and supports a procedural language to control the flow of these commands. The execution of command procedures is controlled directly from the MMI.
The Man-Machine Interface (MMI) is the part of the simulator infrastructure that provides the graphical, user-friendly, configurable interface to any simulator. It enables the user to monitor the simulation as it displays information about the state of the simulator - including log messages, time and mode of the simulator, the schedule and model simulation data. In addition, it provides the user an interface for controlling the simulator by means of commands execution or scripts that act on the simulator.